Exhaust gas collector and gas turbine

ABSTRACT

An exhaust collector for gas turbines, the exhaust collector comprises a plenum with a gas inlet wall, a gas inlet aperture provided in the gas inlet wall, and a gas discharge aperture. The exhaust collector further comprises a plurality of first connectors arranged around the gas inlet aperture and a plurality of second connectors, arranged around the gas inlet aperture. The second connectors are arranged generally opposite the first connectors. The first connectors and second connectors are paired. Pairs of one first connector and one second connector are selectively usable for mounting the exhaust collector on an exhaust diffuser of a gas turbine in a selected one of a plurality of alternative angular positions.

BACKGROUND

Embodiments of the present disclosure generally relate to gas turbine engines and more particularly to exhaust gas collectors or plenums.

Gas turbine engines are widely used as prime movers in mechanical drive applications as well as in power generation. Often, aeroderivative gas turbines are used for these purposes. In mechanical drive applications the gas turbine engine drives one or more turbomachines, e.g. a compressor or a compressor train. In power generation applications the gas turbine engine is used to drive an electric generator connected to an electric distribution grid.

The gas turbine engine combusts a fuel to generate hot combustion gases, which flow through a power turbine to drive a load, e.g., an electrical generator or a compressor. At high velocities and temperatures, an exhaust gas exits the turbine and enters an exhaust gas diffuser and an exhaust gas collector arranged downstream the exhaust gas diffuser.

The exhaust gas collector is usually mounted on and supported by the diffuser. Vibrations of the exhaust gas collector are thus transmitted to the diffuser and to the gas turbine engine bearings.

The exhaust gas collector forms a plenum with an exhaust aperture in fluid communication with an exhaust stack. The exhaust aperture can be oriented vertically upwardly or sideways, depending upon design constraints imposed upon the gas turbine arrangement. The exhaust collector must therefore be designed or adapted each time to the specific orientation of the exhaust aperture.

FIGS. 1 and 2 illustrate a gas turbine engine and an exhaust diffuser-collector arrangement according to the current art. In FIG. 1, a diagram of a gas turbine engine power plant 10 is illustrated. A gas turbine engine 12, for example an aeroderivative gas turbine engine, is coupled to an exhaust diffuser-collector assembly 14. An electrical generator 16 is coupled to the gas turbine engine 12 through a linkage 18. The gas turbine engine 12, the exhaust diffuser-collector assembly 14, and the electrical generator 16 may be securely attached to a skid or base plate 20. Clean air for combustion is supplied by an air intake and filtration system 22. The air is compressed in a compressor section of the gas turbine engine 12 and mixed with a liquid fuel or gas fuel, such as natural gas. The fuel-air mixture is then combusted in a combustion chamber of the gas turbine engine 12. Hot pressurized combustion gas resulting from the combustion of the fuel-air mixture then passes through a plurality of turbine stages in the gas turbine engine 12. The hot pressurized combustion gas will cause the turbine to rotate, driving the load 16 through the linkage 18.

The exhaust diffuser-collector assembly 14 captures and routes the hot exhaust gas for further use, for example by a heat recovery system, or directs the exhaust gas towards an exhaust stack 23.

FIG. 2 illustrates a sectional view of an embodiment of an exhaust diffuser-collector assembly 14 according to the current art. The exhaust diffuser-collector assembly 14 includes an axial exhaust diffuser 24 coupled to a radial exhaust collector 26. The axial exhaust diffuser 24 includes features to at least partially deflect the exhaust gas flow from an axial direction toward a radial direction to enable use of the axial exhaust diffuser 24 with the radial exhaust collector 26. The illustrated axial exhaust diffuser 24 has an annular wall 25, which gradually increases in diameter in a flow direction of exhaust flow from the gas turbine engine 12 toward the radial exhaust collector 26. The smaller diameter end of the axial exhaust diffuser 24 is coupled to the gas turbine engine 12 (only partly shown in FIG. 2). The axial exhaust diffuser 24 diffuses an axial flow of the exhaust gas flowing from the gas turbine engine 12. The radial exhaust collector 26 is attached to the axial exhaust diffuser 24, e.g. by means of a coupling disk 28, by circumferentially bolting the coupling disk 28 to a retaining flange included in a wall 30 of the radial exhaust collector 26. The flange and bolt attachment embodiments enable the axial exhaust diffuser 24 and the radial exhaust collector 26 to remain securely adjoined during the operation of the gas turbine engine 12, while also allowing for maintenance and disassembly during periods of engine inactivity. The radial exhaust collector is sometimes overhung on the axial exhaust diffuser. In other known embodiments, rear legs are provided to support the weight, in combination with a connection to the gas turbine diffuser.

The radial exhaust collector 26 has an inner exhaust plenum or collector chamber with a vertically upwardly oriented aperture 42 provided in a top wall of the exhaust plenum.

SUMMARY OF THE INVENTION

According to some embodiments, an exhaust collector for gas turbines is provided, comprising: a plenum with a gas inlet wall, a gas inlet aperture in the gas inlet wall, and a gas discharge aperture; a plurality of first connectors arranged around the gas inlet aperture; a plurality of second connectors, arranged around the gas inlet aperture, generally opposite the plurality of first connectors. The plurality of first connectors and the plurality of second connectors are paired, i.e. each first connector is arranged opposite a corresponding second connector and vice versa. This arrangement allows pairs of one first connector and one second connector to be selectively used for connecting the exhaust collector to an exhaust diffuser of a gas turbine in a selected one of a plurality of alternative angular positions. The same exhaust collector can thus be arranged in different angular positions with respect to the gas turbine. The orientation of the exhaust gas discharge aperture can thus be selected depending upon layout requirements. Moreover, the angular position of the exhaust collector can be changed during transportation of the gas turbine module, to reduce the overall dimension and the footprint of the module.

According to some embodiments, the connectors are arranged so as to limit the mechanical stresses applied by the exhaust collector to the exhaust diffuser of the gas turbine. Specifically, the load of the exhaust collector can be discharged directly onto the gas turbine skid, while only a limited reaction force is required between the exhaust collector and the exhaust diffuser of the gas turbine, to support the exhaust collector in the correct overhung position.

According to some embodiments, the first connectors are positioned along an arc of a circumference. The second connectors can also be positioned along a respective arc of a circumference. The distance between the first connector and the second connector of each pair is constant, so that the exhaust collector can be selectively connected to the same exhaust diffuser of the gas turbine in any one of a plurality of alternative angular positions.

In some embodiments the first connectors are arranged at a first distance from a center of the gas inlet aperture, and the second connectors are arranged at a second distance from the center of the gas inlet aperture of the exhaust collector. The second distance can be greater than first distance.

The exhaust collector can be comprised of a ring constrained to the gas inlet wall and surrounding the gas inlet aperture. The first connectors can be arranged along said ring. According to some embodiments, the exhaust collector can further comprise a frame constrained to the gas inlet wall, distanced from the gas inlet aperture and opposite the gas discharge aperture. The second connectors can be arranged along said frame. The frame can have a trough or box shape, e.g. extending along an arc of a circumference.

In some embodiments, the plenum comprises a front wall opposite the gas inlet wall. The front wall and the gas inlet wall can be inclined one with respect to the other. The box-shaped or trough-shaped frame can have a variable transverse dimension so as to form a planar surface substantially parallel to the front wall.

According to a further aspect, there is provided a gas turbine comprising a base plate, an exhaust diffuser constrained to the base plate, and an exhaust collector as described above. The exhaust collector is connected to the gas turbine by means of a selected one of the first connectors constrained to the exhaust diffuser and a selected one of the second connectors constrained to the base plate. A major part of the weight of the exhaust collector is thereby supported by said base plate through the second connector. In an embodiment, substantially the entire weight of the exhaust collector is supported by the base plate through the second connector.

Features and embodiments are disclosed here below and are further set forth in the appended claims, which form an integral part of the present description. The above brief description sets forth features of the various embodiments of the present invention in order that the detailed description that follows may be better understood and in order that the present contributions to the art may be better appreciated. There are, of course, other features of the invention that will be described hereinafter and which will be set forth in the appended claims. In this respect, before explaining several embodiments of the invention in details, it is understood that the various embodiments of the invention are not limited in their application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception, upon which the disclosure is based, may readily be utilized as a basis for designing other structures, methods, and/or systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 illustrates a side view of a power generator plant with a gas turbine engine of the current art;

FIG. 2 illustrates a section of an exhaust diffuser-collector assembly of the current art;

FIG. 3 illustrates a side schematic view of a power generator plant with a gas turbine engine according to one embodiment of the present disclosure;

FIG. 4 illustrates an enlarged side view and partial section of the exhaust diffuser-collector assembly of the system of FIG. 3;

FIG. 5 illustrates an enlargement of FIG. 4;

FIG. 6 illustrates a detail of the connection of the exhaust collector to the gas turbine base plate;

FIG. 7 illustrates an enlargement of detail VII in FIGS. 8 and 9, of the connection between the exhaust collector and the exhaust diffuser; and

FIGS. 8 and 9 illustrate perspective views of alternative positions of the exhaust collector on the gas turbine base plate.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The following detailed description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Additionally, the drawings are not necessarily drawn to scale. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase “in one embodiment” or “in an embodiment” or “in some embodiments” in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

In FIG. 3, a diagram of a gas turbine engine power plant 110 for the production of electric power is illustrated. This system is provided just as an exemplary embodiment of a possible application of the subject matter disclosed herein. The features of an exhaust collector as described herein and the advantages thereof can be exploited in different gas turbine systems, e.g. for mechanical drive applications, where the gas turbine engine is used to drive a load such as a turbomachine, e.g. a compressor or a compressor train.

Turning now again to the exemplary embodiment of FIG. 3, a gas turbine engine, briefly also indicated as gas turbine 112, for example an aeroderivative gas turbine engine, is coupled to an exhaust diffuser-collector assembly 114. An electrical generator 116 is coupled to the gas turbine engine 112 through a linkage 118. The gas turbine engine 112, exhaust diffuser-collector assembly 114, and electrical generator 116 may be securely attached to a skid or base plate 120. Clean air for combustion is supplied by an air intake and filtration system 122. The air is compressed in a compressor section of the gas turbine engine 112 and mixed with a liquid fuel or gas fuel, such as natural gas. The fuel-air mixture is then combusted in a combustion chamber of the gas turbine engine 112. Hot pressurized combustion gas resulting from the combustion of the fuel-air mixture then passes through a plurality of turbine stages in the gas turbine engine 112. The hot pressurized combustion gas will cause the turbine to rotate, driving the load 116 through the linkage 118.

The exhaust diffuser-collector assembly 114 captures and routes the hot exhaust gas for further use, for example by a heat recovery system, or directs the exhaust gas towards an exhaust stack 123.

The features of the exhaust diffuser-collector arrangement 114 will now be described in greater detail reference being made to FIGS. 4-9.

In FIG. 4 only the last portion of the gas turbine engine 112 is depicted, namely the power turbine. The exhaust diffuser-collector assembly 114 is arranged downstream the gas turbine engine 112. The exhaust diffuser-collector assembly 114 may comprise an axial exhaust diffuser 124 coupled to a radial exhaust collector 126. The axial exhaust diffuser 124 includes features to at least partially deflect the exhaust gas flow from an axial direction toward a radial direction to enable use of the axial exhaust diffuser 124 with the radial exhaust collector 126. These features will not be described in detail herein, since they are well known to those of ordinary skill in the art.

The illustrated axial exhaust diffuser 124 has an annular wall 125, which gradually increases in diameter in a flow direction F of exhaust flow from the gas turbine engine 112 toward the radial exhaust collector 126. The smaller diameter end of the axial exhaust diffuser 124 is coupled to the gas turbine engine 112 (only partly shown in FIG. 4). The axial exhaust diffuser 124 diffuses an axial flow of the exhaust gas flowing from the gas turbine engine 112. The radial exhaust collector 126 is attached to the gas turbine baseplate 120 and to the axial exhaust diffuser 124 as will be described in greater detail here below.

The axial exhaust diffuser 124 can be constrained to the gas turbine skid or base plate 120 by means of a pair of brackets 128. The axial exhaust diffuser 124 can be hinged at said two brackets 128 about a transverse horizontal axis B-B (FIGS. 8 and 9). A gib 130 can further be provided, wherein the exhaust diffuser is freely slidably arranged. The gib 130 provides a transversal reaction force in case of rotor unbalancing.

The exhaust diffuser 124 may comprise a terminal annular flange or ring 127 arranged at the larger diameter end, facing the exhaust collector 126. The annular flange 127 substantially surrounds the exhaust diffuser outlet. In the uppermost position of the annular flange 127 a first connector member 129 is constrained to the exhaust diffuser 124. One exemplary embodiment of the first connector member 129 is illustrated in detail in FIG. 7. The first connector member 129 can comprise a plate 131 screwed to the annular flange 127 by means of a plurality of screws 133. A shim 134 can be provided between the plate 131 and the annular flange 127. The plate 131 can be rigidly constrained to or monolithically formed with an appendage 137 projecting in a substantially radial direction from the annular flange 127. The appendage 137 forms part of a first connection arrangement for connecting the exhaust collector 126 to the exhaust diffuser 124 as will be described in greater detail later on.

The exhaust collector 126 comprises a gas inlet wall 135 and an opposite front wall 138, opposite said gas inlet wall 135. The gas inlet 135 wall is oriented towards the exhaust diffuser 124 and is provided with a gas inlet aperture 139. A collector chamber or collector plenum 141 can be provided in the exhaust collector 126. The collector chamber 141 can be bounded by the gas inlet wall 135, by the front wall 138 and by a side wall 143 (FIGS. 8 and 9). The side wall 143 can be opened at 143A forming a gas discharge aperture 143A. In the exemplary embodiment the gas discharge aperture 143A is rectangular.

In some embodiments, the gas inlet wall 135 and the front wall 138 of the exhaust collector are non-parallel. The gas inlet wall 135 and the front wall 138 can be inclined one with respect to the other in a converging-diverging arrangement, so that the collector chamber 141 has a dimension, in the axial direction of the gas turbine, which decreases from the gas discharge aperture 143A towards the end of the collector chamber 141 opposite said gas discharge aperture 143A.

The inner volume of the collector chamber 141 can be annular. In the collector chamber 141 a central wall 145 can be arranged. In some embodiments, the central wall has the shape of a solid of revolution. In the embodiment shown in the drawings the central wall 145 has a frustum-conical shaped portion 145A and is connected at the large-diameter end of said frustum-conical portion to the front wall 138 by a rounded wall portion 145B. The central wall 145 extends through the inlet gas aperture 139, substantially coaxially to the rotation axis A-A of the gas turbine engine 112.

A substantially cylindrical sleeve 147 can be introduced in the gas inlet aperture 139 and rigidly constrained to the gas inlet wall 135. The sleeve 147 is substantially coaxial with the central wall 145 so that an annular gas inlet passage is thus formed between the central or inner wall 145 and the sleeve 147, said annular gas inlet passage placing in fluid communication the interior of the exhaust diffuser 124 with the collector chamber 141.

Along the end of the sleeve 147 facing the gas turbine engine 112 an inner flange 149 is provided. Along the inner flange 149 a plurality of pairs of holes 151 are arranged. In some embodiments three pairs of holes 151 can be arranged, spaced from one another by approx. 45°. As will be explained in greater detail below, one of said hole pairs can be selected for attaching the exhaust collector to the gas turbine engine in a selected angular position.

Each pair of holes 151 can be used for anchoring the exhaust collector 126 to the exhaust diffuser 124 by means of the appendage 137. As shown in the enlargement of FIG. 7, connection between the exhaust collector 126 and the appendage 137 is made by a fork-shaped component 153, which can be screwed to the inner flange 149 by means of two screws 155 engaging the selected pair of holes 151. The fork-shaped component 153 is arranged so that the two prongs thereof are located on the two sides of the appendage 137. A fixing plate 157 is screwed to the opposed prongs of the fork-shaped component 153 to form a closed frame surrounding the appendage 137. The fork-shaped component 153 along with the appendage 137 form the first connection member for connecting the exhaust collector 126 to the exhaust diffuser 124.

The pairs of holes 151 are arranged along a circumference at a constant distance from the axis of the sleeve 147 and therefore from the axis of the annular gas inlet passage formed by the coaxially arranged sleeve 147 and central wall 145. The exhaust collector 126 can therefore be latched on to the appendage 137 in any one of the plurality of angular positions defined by the pairs of holes 151, in each position the exhaust collector 126 being substantially coaxial with the exhaust diffuser 124.

The pairs of holes 151 thus form a plurality of first connectors for connecting the exhaust collector 126 to the gas turbine engine 112 and more specifically to the exhaust diffuser 124 thereof.

The exhaust collector 126 can be further provided with a plurality of second connectors, arranged for connecting the exhaust collector 126 to the base plate or skid 120 of the gas turbine engine 112. In some embodiments said plurality of second connectors can be arranged along a circumference centered on the axis of the gas turbine engine 112 and on the axis of the annular gas inlet passage between the sleeve 147 and the central wall 145. As shown e.g. in FIGS. 8 and 9, a frame 161 is attached to the outer surface of the gas inlet wall 135. The frame can have a semi-circular shape and be centered on the axis A-A of the gas turbine engine 112 when the exhaust collector 126 is mounted on the exhaust diffuser 124. In other embodiments, the frame 161 can extend around less than a semi-circumference, e.g. by 90°. In general the frame 161 is positioned opposite the pairs of holes 151 with respect to the axis A-A of the gas turbine engine 112.

Along the frame 161 a plurality of second connectors is provided, the number of said second connectors being equal to the number of said first connectors. Thus, for each pair of holes 151 a second connector on the frame 161 is provided. Each second connector can comprise a hole 163 in the frame 161. The angular pitch between the holes 161 is the same as the angular pitch between the pairs of holes 151. Pairs of first and second connectors are therefore formed. Each first connector 151 corresponds to a second connector 163 and the distance between paired first and second connectors 151, 163 is constant.

Each second connector can co-act with a second connection member 171 provided for connecting the exhaust collector 126 to the gas turbine engine 112 and to the exhaust diffuser 124. The second connection member 171 is constrained to the base plate or skid 120 of the gas turbine engine 112.

The second connection member 171 can comprise a substantially horizontally extending pin 173, which can be introduced selectively into one or the other of said holes 161 forming the second connectors on the exhaust collector side. The pin-hole arrangement thus obtained forms a constraint between the exhaust collector 126 and the skid or base plate 120, which is capable of supporting vertical loads. In addition to the mechanical connection provided by the pin-hole connection described above, the second connection member 171 can further comprise a plate 175 with through holes, for screwing the plate 175 to a counter-plate 177 arranged inside the frame 161. This screw connection provides for additional stability of the link between the skid or base plate 120 and the exhaust collector 126.

The frame 161 can be box-shaped. In some embodiments, the frame 161 can have a rectangular or U-shaped cross section, as shown in particular in FIG. 5. The counter-plate 177 arranged in the frame 161 can be housed in the empty space formed by the box-shaped structure of the frame. The counter-plate 177 can be fixed and extend along the entire extension of the frame 161. It can be provided with threaded holes, e.g. four threaded holes, for screws 179.

When the gas inlet wall 135 is inclined (non-orthogonal) with respect to the axis of the gas turbine engine 112, as in the exemplary embodiment shown in the drawings, the box-shaped frame 161 has a shape such that the surface 161A of the frame 161 where the holes 163 are provided is orthogonal to the gas turbine axis A-A when the exhaust collector is in the assembled condition.

The plurality of first and second connectors 151, 163 provided around the annular gas inlet passage of the exhaust collector allow the exhaust collector to be connected to the base plate or skid 120 and to the exhaust diffuser 124 in one of several angular positions. Two such angular positions are shown in FIGS. 8 and 9. In FIG. 8 the exhaust collector 126 is mounted such that the gas discharge aperture 143A is oriented vertically upwardly. In FIG. 9 the exhaust collector 126 is mounted with the gas discharge aperture 143A oriented sideways in a horizontal direction. The two positions are thus angularly shifted by 90°. Either one or the other of said two positions can be selected, depending upon the location of the exhaust stack 123, for instance. If the exhaust stack 123 is arranged above the gas turbine engine 112, the configuration of FIG. 8 is chosen. If the exhaust stack is arranged sideways of the gas turbine engine, the configuration of FIG. 9 would be applicable. Further angular positions are possible. For example a further position, where the gas discharge aperture 143A is oriented horizontally but opposite to the position of FIG. 9, can be obtained by rotating the exhaust collector by 180° with respect to the arrangement of FIG. 9, e.g. if the exhaust stack is arranged on the opposite side of the gas turbine engine 112.

In some embodiments, the exhaust collector can have a first smaller transverse dimension and a second, larger transverse dimension. In FIG. 8 the exhaust collector 126 is mounted with the smaller transverse dimension oriented horizontally, while in FIG. 9 the horizontal dimension is the larger one. If the configuration of FIG. 9 is selected, transportation of the gas turbine engine module, including the gas turbine engine 112 and the skid 120, can be made with the exhaust collector 126 in the configuration of FIG. 8 to reduce the horizontal cross dimension of the module and render transportation easier. On site the exhaust collector can be disengaged from the exhaust diffuser, rotated by 90° and re-assembled in the final configuration of FIG. 9.

The arrangement and configuration of the first connectors and second connectors is such that once mounted the lower constraint, provided by the second connection member 171 on the skid or base plate 120 and the respective second connector on the exhaust collector, said lower constraint transmits both horizontal as well as vertical constraint forces. Substantially the entire weight of the exhaust collector is thus transmitted through the second connector to the skid or base plate of the gas turbine, rather than to the exhaust diffuser. Vibrations generated in the exhaust collector generate constraint stresses on the lower constraint between the exhaust collector 126 and the skid or base plate 120, and do not negatively affect the bearings or other components of the turbomachine 112. The direct link between the exhaust collector 126 and the exhaust diffuser 124, provided by the first connection member 137, 153 and the selected first connector 151 on the exhaust collector 126 is such that only horizontal forces, but no vertical loads, are transmitted directly from the exhaust collector 126 to the exhaust diffuser 124. The exhaust diffuser remains therefore broadly free of additional loads, both static as well as dynamic, generated by the exhaust collector 126. More specifically, since the exhaust collector 126 is mounted in a cantilever fashion, i.e. overhung with respect to the base plate 120, a limited horizontal constraint force is provided by the upper constraint provided by the first connection member, said horizontal constraint force generating a momentum sufficient to balance the momentum generated by the weight of the exhaust collector 126.

While the disclosed embodiments of the subject matter described herein have been shown in the drawings and fully described above with particularity and detail in connection with several exemplary embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without materially departing from the novel teachings, the principles and concepts set forth herein, and advantages of the subject matter recited in the appended claims. Hence, the proper scope of the disclosed innovations should be determined only by the broadest interpretation of the appended claims so as to encompass all such modifications, changes, and omissions. In addition, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. 

What is claimed is:
 1. An exhaust collector for gas turbines, comprising: a plenum with a gas inlet wall; a gas inlet aperture in the gas inlet wall; a gas discharge aperture; a plurality of first connectors arranged around the gas inlet aperture; and a plurality of second connectors, arranged around the gas inlet aperture, generally opposite the plurality of first connectors, wherein the plurality of first connectors and the plurality of second connectors are paired, and wherein pairs of one first connector and one second connector are selectively usable for mounting the exhaust collector on an exhaust diffuser of a gas turbine in a selected one of a plurality of alternative angular positions.
 2. The exhaust collector according to claim 1, wherein: the first connectors are positioned along an arc of a circumference, the second connectors are positioned along an arc of a circumference, and the distance between the first connector and the second connector of each pair being constant.
 3. The exhaust collector according to claim 1, wherein the first connectors are arranged at a first distance from a center of the gas inlet aperture, and the second connectors are arranged at a second distance from the center of the gas inlet aperture.
 4. The exhaust collector according to claim 1, further comprising a ring constrained to the gas inlet wall and surrounding the gas inlet aperture, the plurality of first connectors being arranged along the ring.
 5. The exhaust collector according to claim 1, further comprising a frame constrained to the gas inlet wall, distanced from the gas inlet aperture and opposite the gas discharge aperture, the plurality of second connectors being arranged along the frame.
 6. The exhaust collector according to claim 5, wherein the frame is box-shaped.
 7. The exhaust collector according to claim 6, wherein: the plenum comprises a front wall opposite the gas inlet wall, the front wall and the gas inlet wall are inclined one with respect to the other, and the box-shaped frame has a variable transverse dimension forming a planar surface substantially parallel to the front wall.
 8. The exhaust collector according to claim 1, wherein the first connectors are designed and configured to support horizontal loads but not vertical loads.
 9. The exhaust collector according to claim 1, wherein the second connectors are designed and configured to support vertical loads.
 10. The exhaust collector according to claim 1, wherein each first connector comprises holes for screw-connection of a fork-shaped component.
 11. The exhaust collector according to claim 1, wherein each second connector comprises a hole.
 12. The exhaust collector according to claim 1, wherein the first connectors are distribute along an arc of at least approximately 90°, and the second connectors are distribute along an arc of at least approximately 90°.
 13. A gas turbine comprising: a base plate; an exhaust diffuser constrained to the base plate; and an exhaust collector comprising: a plenum with a gas inlet wall; a gas inlet aperture in the gas inlet wall; a gas discharge aperture; a plurality of first connectors arranged around the gas inlet aperture; and a plurality of second connectors, arranged around the gas inlet aperture, generally opposite the plurality of first connectors, wherein the plurality of first connectors and the plurality of second connectors are paired, and wherein pairs of one first connector and one second connector are selectively usable for mounting the exhaust collector on an exhaust diffuser of a gas turbine in a selected one of a plurality of alternative angular positions, wherein the exhaust collector is connected to the gas turbine by one of the first connectors constrained to the exhaust diffuser and one of the second connectors constrained to the base plate.
 14. The gas turbine according to claim 13, wherein weight of the exhaust collector is substantially entirely supported by the base plate through the second connector.
 15. The gas turbine according to claim 13, wherein: the exhaust diffuser comprises a first connection member configured and arranged for co-action with a selected one of the first connectors, and the base plate comprises a second connection member configured and arranged for co-action with a selected one of the second connectors.
 16. The gas turbine according to claim 15, wherein the first connection member is arranged on the exhaust diffuser, opposite the base plate.
 17. The gas turbine according to claim 15, wherein the second connection member comprises a pin selectively engaging into a corresponding hole of a selected one of the second connectors.
 18. The exhaust collector according to claim 1, wherein the first connectors are distribute along an arc of at least approximately 180°, and the second connectors are distribute along an arc of at least approximately 180°. 